import java.util.LinkedList;
import java.util.Queue;
import java.util.Stack;

/**
 * E要具有可比较性
 * Created by brss on 2018/9/12.
 */
public class BST<E extends Comparable<E>> {
    private class Node{
        public E e;
        public Node left,right;

        public Node(E e) {
            this.e = e;
            left = null;
            right = null;
        }
    }

    private Node root;
    private int size;

    public BST(){
        root = null;
        size = 0;
    }

    public int getSize(){
        return size;
    }
    public boolean isEmpty(){
        return size==0;
    }

    //向二分搜索树中添加新的元素
    public void add(E e) {
        root = add(root, e);
    }

    //向以node为根的二分搜索树中添加元素E，递归算法
    //返回插入新节点后二分搜索树的根
    private Node add(Node node, E e) {
        //终止条件
        if (node == null) {
            size++;
            return new Node(e);
        }
        //递归调用
        if (e.compareTo(node.e) < 0)
            node.left = add(node.left,e);
        else if (e.compareTo(node.e) > 0)
            node.right = add(node.right,e);

        return node;
    }

    //看二分搜索树中是否包含元素e
    public boolean contains(E e) {
        return contains(root,e);
    }

    //看以node为根的二分搜索树中是否包含e，递归算法
    private boolean contains(Node node, E e) {
        if (node==null)
            return false;

        if (e.compareTo(node.e) < 0) {
            return contains(node.left,e);
        } else if (e.compareTo(node.e) > 0) {
            return contains(node.right,e);
        }else {//等于时的情况
            return true;
        }
    }

    //二分搜索树的前序遍历
    public void preOrder(){
        preOrder(root);
    }

    //前序遍历以node为根的二分搜索树，递归算法
    private void preOrder(Node node) {
        if (node == null)
            return;
        System.out.println(node.e);
        preOrder(node.left);
        preOrder(node.right);
    }

    //二分搜索树的非递归前序遍历
    public void preOrderNR(){
        Stack<Node> stack = new Stack<>();
        stack.push(root);
        while (!stack.isEmpty()) {
            Node cur = stack.pop();
            System.out.println(cur.e);
            if (cur.right != null)
                stack.push(cur.right);
            if (cur.left != null)
                stack.push(cur.left);
        }
    }

    //二分搜索树的中序遍历
    public void inOrder(){
        inOrder(root);
    }

    //中序遍历以node为根的二分搜索树，递归算法
    private void inOrder(Node node) {
        if (node == null)
            return;
        inOrder(node.left);
        System.out.println(node.e);
        inOrder(node.right);
    }

    //二分搜索树的后序遍历
    public void postOrder(){
        postOrder(root);
    }

    //后序遍历以node为根的二分搜索树，递归算法
    private void postOrder(Node node) {
        if (node == null)
            return;
        postOrder(node.left);
        postOrder(node.right);
        System.out.println(node.e);
    }

    // 二分搜索树的层序遍历
    public void levelOrder(){
        Queue<Node> q = new LinkedList<>();
        q.add(root);
        while (!q.isEmpty()) {
            Node cur = q.remove();
            System.out.println(cur.e);

            if (cur.left != null)
                q.add(cur.left);
            if (cur.right != null)
                q.add(cur.right);
        }
    }

    // 寻找二分搜索树的最小元素
    public E minimum(){
        if (size == 0)
            throw new IllegalArgumentException("BST is empty");

        return minimum(root).e;
    }
    //返回以node为根的二分搜索树的最小值所在的节点
    private Node minimum(Node node){
        if (node.left == null)
            return node;
        return minimum(node.left);
    }

    // 寻找二分搜索树的最大元素
    public E maximum(){
        if (size == 0)
            throw new IllegalArgumentException("BST is empty");
        return maximum(root).e;
    }

    //返回以node为根的二分搜索树的最大值所在节点
    private Node maximum(Node node) {
        if (node.right == null)
            return node;
        return minimum(node.right);
    }

    //从二分搜索树中删除最小值所在节点，返回最小值
    public E removeMin(){
        E ret = minimum();
        root = removeMin(root);
        return ret;
    }

    //删除掉以node为根的二分搜索树中的最小节点
    //返回删除节点后新的二分搜索树的根
    private Node removeMin(Node node) {
        if (node.left == null){
            Node rightNode = node.right;
            node.right = null;
            size--;
            return rightNode;
        }
        node.left = removeMin(node.left);
        return node;
    }

    // 从二分搜索树中删除最大值所在节点
    public E removeMax(){
        E ret  = maximum();
        root = removeMax(root);
        return ret;
    }

    //删除以node为根的二分搜索树中最大值节点
    //返回删除节点后新的二分搜索树的根
    private Node removeMax(Node node) {
        if (node.right == null) {
            Node leftNode = node.left;
            node.left = null;
            size--;
            return leftNode;
        }

        node.right = removeMax(node.right);
        return node;
    }

    //从二分搜索树中删除元素e的节点
    public void remove(E e) {
        root = remove(root, e);
    }

    //删除以node为根的分搜搜搜搜中值为e的节点，递归算法
    //返回删除节点后新的二分搜索树的根
    private Node remove(Node node, E e) {
        if (node == null)
            return node;

        if (e.compareTo(node.e) < 0) {
            node.left = remove(node.left, e);
            return node;
        } else if (e.compareTo(node.e) > 0){
            node.right = remove(node.right, e);
            return node;
        }else { // e == node.e
            //待删除节点的右子树不为空的情况
            if (node.left == null) {
                Node rightNode = node.right;
                node.right = null;
                size--;
                return rightNode;
            }
            //待删除节点的左子树不为空的情况
            if ( node.right == null) {
                Node leftNode = node.left;
                node.left = null;
                size--;
                return leftNode;
            }
            //待删除节点的左右子树都不为空的情况
            // 找到比待删除节点大的最小节点，即待删除节点右子树的最小节点
            // 用这个节点顶替待删除节点的位置

            Node successor = minimum(node.right);//后继节点（比待删除节点大的最小节点）
            successor.right = removeMin(node.right);
            successor.left = node.left;
            //size--;在removeMin时做过size--这个操作的
            node.left = node.right = null;
            return successor;
        }

    }
    @Override
    public String toString(){
        StringBuilder res = new StringBuilder();
        generateBSTString(root, 0, res);
        return res.toString();
    }

    //生成以node为根结点，深度为depth的描述二叉树的字符串
    private void generateBSTString(Node node, int depth, StringBuilder res) {
        if (node == null) {
            res.append(generateDepthString(depth) + "null\n");
            return;
        }
        res.append(generateDepthString(depth) + node.e + "\n");
        generateBSTString(node.left, depth + 1, res);
        generateBSTString(node.right, depth + 1, res);
    }

    private String generateDepthString(int depth) {
        StringBuilder res = new StringBuilder();
        for (int i = 0 ; i < depth ; i++) {
            res.append("--");
        }
        return res.toString();
    }

}
